1. Field of the Invention
The present invention relates to a crusher bucket with a crushing lid for recycling lumps of asphalt, scraps of concrete, etc. More particularly, the present invention relates to a crusher bucket attached to the distal end of an arm of a civil engineering machine and having the function of crushing raw materials. Even more particularly, the present invention pertains to a crusher bucket with a crushing lid improved in maintainability and productivity.
2. Discussion of Related Art
A civil engineering machine that is generally called “impact crusher” crushes and grinds material to be crushed (raw material) such as industrial waste, i.e. concrete scraps, asphalt paving mixture, aggregate for civil engineering and construction applications, or crushed stone. The crushed materials are reused as recycling materials. The impact crusher has a rotor with a horizontal axis in a casing. The rotor has a plurality of hammers radially arranged thereon. Material to be crushed is loaded into the crusher with the rotor rotating. The material is impacted between the rotor and a repulsion plate secured to the casing inner surface, thereby being crushed. The hammers mounted on the rotor are always in direct contact with the raw material under impact force. Therefore, the distal end portions of the hammers wear out as the service time of the crusher elapses.
Generally, the distal end portions of the hammers become worn out to a considerable extent when a predetermined time has elapsed. As a result, the crushing efficiency degrades markedly. Meanwhile, if a large amount of material to be crushed is fed at a time into the crushing chamber in which the hammers are rotating, the material is likely to be caught between the casing body (the bucket body) and the hammers, causing an interruption of the crushing operation. If the material to be crushed gets caught in this way, it becomes necessary to perform an operation of disassembling the hammers to release and remove the caught material. Regarding the hammer mounting structure, the present applicant proposed a technique whereby after a hammer has been inserted into a cut portion of a rotor body, an engaging projection is fitted into an engaging hole formed in a retaining block to support the hammer, and the retaining block is supported between support members, thereby securing the hammer [see Japanese Utility Model Unexamined Publication (KOKAI) No. Hei 4-45547 and Japanese Patent Unexamined Publication (KOKAI) No. 2001-190972].
The hammers of stationary impact crushers are stationary. There is, however, known a small-sized crusher in which hammers are pivotably supported on pivot shafts to crush raw material by the pivotal motion of the hammers. The pivoted hammers can be used also as members for mixing clayish soil with air or a soil conditioner, e.g. a stabilizer, and stirring the mixture. Replacement of the hammers is generally made by removing the pivot shafts pivotably supporting the hammers.
Conventionally, scrap materials such as asphalt lumps are reprocessed at a site where a recycling plant is installed. This method requires a great deal of energy, time and cost to transport scrap materials from the site where they are generated to the reprocessing site. Therefore, there have recently been proposed methods wherein a small amount of recyclable material is directly reprocessed at a site where it is generated. Among these are methods wherein recyclable material is reprocessed in a bucket of a civil engineering machine. Many proposals have been made regarding the method and structure of crushing in the crusher bucket [for example, see Japanese Patent Unexamined Publication (KOKAI) Nos. Hei 9-88355, Hei 10-30247 and 2001-113198].
When material to be crushed gets caught between the crusher hammers and the casing body, an operation of removing and remounting the hammers and so forth has to be performed to release and remove the caught material. When becoming worn or damaged, the hammers need to be replaced with new ones. The hammer replacing operation plus the hammer removing and remounting operation increases downtime for maintenance and degrades productivity. Further, impact hammers require the hammer replacing operation to be carried out relatively frequently. Because these hammers are small in size, the space for the replacing operation is narrow and it is difficult to perform the operation. Therefore, the hammer removing or replacing operation has to be done as efficiently as possible. In the case of pivoted impact hammers, in particular, the pivot shafts need to be removed in order to replace the hammers, and it is necessary to temporarily remove another hammer that is provided on the same pivot shaft as the one to be replaced and that need not be replaced.
Thus, there has been a demand for development of a crusher bucket with a crushing lid improved in maintainability and productivity. More specifically, it has been demanded to provide a crusher bucket arranged so that material to be crushed will not easily be caught between the bucket body and the hammers, etc., thereby minimizing the likelihood of occurrence of an event requiring the material removing operation, and in the event that material to be crushed gets caught, the hammer removing and remounting operation can be readily performed to remove the caught material.